1. Field of the Invention
The present invention is directed to a miniature switch, and more particularly to an improved miniature snap action switch of compact size and extended operating life.
2. Description of the Prior Art
In the miniature switches which have been widely provided, it is customary to utilize a snap action spring with movable contacts for movement into and out of contact with cooperative fixed contacts, as exemplarily shown in FIG. 4. The miniature switch of this type comprises a base 1 mounting thereon a common contact member 2, separate contact carriers 3 and 4, and a snap action spring 5 with movable contact tips 6 and 7. The snap action spring 5 is pivotally supported to the common contact member 2 so that the free end portion carrying said movable contact tips 6 and 7 is movable with a snap action between a pair of vertically spaced fixed contacts 8 and 9 for alternate contact with the fixed contacts 8 and 9 in response to being depressed by a plunger 40 and released therefrom. Each of the movable contact tips 6 and 7 is attached onto the snap action spring 5 by being staked or welded thereto. In the miniature switch of the above structure, however, the snap action spring comprises a spring sheet of extremely small thickness, for example, 0.05 mm which makes it difficult to weld or stake the tip on the spring sheet. Further, the tip even successfully welded or staked is of bulky configuration which is larger dimensions in physical size than required for this type of the miniature switch with respect to its current passing capacity, such tip adding considerably to the thickness of the spring sheet with the tip, thus requiring an increased distance between the fixed contacts and therefore the increased height of the contact assembly, thereby resulting in an undesirably increased height of the miniature switch, which opposes the miniaturization of the switch. In addition to the above problem, there arises another problem that the snap action spring is liable to deform or adversely change its spring characteristics when subjected to heat or pressure due the welding or staking operation, which is undesirable for the miniature switch of precision character and is therefore should be eliminated for the purpose of providing a reliable miniature switch over a longer operating life.